A bowline knot is an excellent rescue knot as it tightens when under load. However, its very use as a rescue knot may make it hard to tie - for example, if a person fell and damaged one arm to the point where he or she was unable to use it to help tie a knot!

My favorite way to tie a bowline is a little unorthodox, but it's easier, especially 1-handed.

Make a slipknot in the standing part.

Grab the standing part.

Twist to make a loop.

Reach through the loop and grab the standing part.

Pull the standing part through the loop.

Pass the working end through the slipknot.

Capsize the slipknot.

Now you have a bowline. It may be left- for right-handed, depending on the direction you did step #2. One is slightly more reliable, but both are good knots. You can improve the reliability by hitching the loose end to the loop. For critical (human) loads, and in slippery (synthetic) line, that hitch is more important.

Be sure to practice this a few times before you need it. The slipknot needs to be snugged up but not tight. You need to know where to put the slipknot to get a big enough loop at the end.

One way this approach is really useful is when you will need to hitch to something very quickly. You can prepare the slipknot ahead of time. When the time comes, pass the working end around the object, through the slipknot, and capsize.